ARSENOMOLYBDIC  AGIU  AS  AN 
ALKALOIDAL  REAGENT 


HY 


GEORGE  SEARLES  SPILVER 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

LIBERAL  ARTS  AND  SCIENCES 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/arsenomolybdicacOOspil 


UNIVERSITY  OF  ILLINOIS 


..ig3.2... 

THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

GE0RGF..SMRLES...5PTLYKB 

ENTITLED ARSE NOMO L.YBDI  C . . A C J D . . A.  § . .AIL .AM A LQ.I.P.A L. . . REAGO.T 


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF  BACHELOROF  SCIENCE.  JN..MBEHA.I-....A.RTS.. AU.D...SC.IM.CES 


Approved  

HEAD  OF  DEPARTMENT  OF pH^ISTRY 


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c 

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Acknowledgment 

The  writer  desires  to  take  this  opportunity 
to  express  his  appreciation  of  the  help  and  guidance  given  by 
Dr.  G.D.  Beal  in  the  preparation  of  this  thesis. 


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Index 


Page 


I.  Introduction  1 

II.  Preparation  2 

III.  Analysis  and  Calculations  3 

IV.  Arseno-molybdic  Acid  as  a Qualitative 

Reagent  for  Alkaloids 10. 

V.  Conclusion  12 

VI . Bibliography  13 


1 


Arsenomolybdic  Acid  as  an 
Alkaloidal  Reagent 


I 

Intrcduct ion 

It  has  been  the  purpose  of  this  work  to  prepare  arsenomoly- 
bic  acid,  to  determine  its  formula,  and  to  investigate  its  value 
as  an  alkaloidal  precipitant. 

V/ork  on  arsenomolybdic  acid  as  an  alkaloidal  reagent  is  not 
found  in  the  literature  to  date.  However,  Seybertfcr’  gives  the 
preparation  and  some  reactions  of  an  ammonium  salt  of  arsenomoly- 
bic  acid.  Freidheim^  also  gives  the  analysis  of  salts  prepar- 
ed by  the  action  of  molybdic  anhydride  on  ammonium  arsenate  and 
of  ammonium  molybdate  on  ammonium  arsenate. 

In  this  work  the  method  of  treating  an  acid  solution  of 
ammonium  molybdate  with  arsenic  acid,  and  also  by  salting  out 
from  this  solution  with  ammonium  salt  was  used  in  the  preparation. 


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2 


II 

Preparation 

One  hundred  grains  of  molybdic  acid  were  dissolved  in  50C 
cc  of  2.5/n  ammonia.  This  solution  was  then  very  slowly  added 
with  constant  stirring,  to  1000  cc  of  6.3/n  nitric  acid,  the 
temperature  of  the  mixture  being  maintained  at  zero  degrees 
centigrade  throughout  the  addition.  A soultion  of  forty 
grams  of  sodium  arsenate  slightly  acidified  with  nitric  acid 
was  then  added,  and  the  mixture  was  heated  on  a water  bath 
at  from  50  to  60  degrees  centigrade.  Heating  continued  at 
this  temperature  for  24  hours  produced  about  25  grams  of  fine 
light  yellow,  crystalline  precipitate  which  was  then  filtered 
of  f . 

The  addition  of  300  grams  of  ammonium  nitrate,  which  with 
the  50  grams  ( approximately)  resulting  from  the  previous  neu- 
tralization, made  a total  of  350  grams  in  the  two  liters  of 
solution,  caused  the  precipitation  in  the  course  of  8 hours  at 
the  same  temperature  of  some  50  grams  of  cyrstals.  This  yield 
was  of  a slightly  darker  yellow  than  that  obtained  previously. 
The  further  addition  of  100  grams  of  ammonium  nitrate  and  con- 
tinued heating  ysilded  now  about  20  grams  of  precipitate  after 
8 hours.  After  standing  several  days  about  10  grams  more 


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3. 


precipitate  was  filtered  from  this  same  solution. 

Still  two  more  filtrations  were  made  of  this  solution 
after  it  had  stood  in  each  case  about  one  week  at  room  tem- 
perature, and  each  time  about  1C  grams  were  obtained.  The 
six  yields  varied  in  color  from  a light  yellow  ( first)  to 
a somewhat  brighter  yellow(  last  sample).  However,  the  vari- 
ation in  shade  being  greatest  between  samples  one  and  two. 

It  will  be  recalled  that  sample  one  was  obtained  before  salt- 
ing out.  These  samples  obtained  by  the  several  filtrations 
were  kept  in  separate  containers  in  order  that  separate  analy- 
sis of  them  would  be  possible. 

In  the  course  of  the  procedure  it  was  noted  that  if  the 
acid  mixture  from  which  the  yellow  crystals  were  precipitated, 
was  slowly  neutralized  with  ammonia,  the  molybdic  acid  would 
be  precipitated  instead  of  the  desired  product. 

Ill 

Analysis 

The  product,  after  drying  was  examined  under  the  micro- 
scope and  found  to  appear  homogeneous,  altho  the  several  sam — 
pies  differed  somewhat  in  size  of  the  crystals. 

The  following  qualitative  tests  were  made:  the  precipita- 
tion of  magnesium  ammonium  arsenate  by  magnesia  mixture  indicat 


' : 1 11 


. 


* 


: 


4. 


ed  the  presence  of  arsenic;  warming  the  substance  with  sodium 
hydroxide  and  testing  the  vapor  with  wet  litmus  paper  indicated 
the  presence  of  the  ammonium  radical;  reduction  to  various  shades 
of  blue  or  blue  green  indicated  the  presence  of  molybdenum, 

A quantitative  analysis  for  these  substances  was  conduct- 
ed as  follows: 

1.  Determination  of  Arsenic  content.  Half  gram  samples 
of  the  ammonium  arsenomolybdate  were  dissolved  each  in  100  cc . of 
water,  treated  with  5 cc . of  concentrated  hydrochloric  acid. 
Twenty-five  cc.  of  magnesia  mixture  was  added,  and  after  neutral- 
ization with  10$  ammonium  hydroxide,  an  excess  of  l/3  the  volume 
of  the  neutralized  solution  was  added.  After  standing  24  hours 
the  solution  was  filtered  through  a Gooch  ( asbestos)  crucible, 
the  precipitate  was  washed  with  2.5$  ammonium  hydroxide,  and 
dried  at  100°  centigrade.  The  precipitate  was  then  ignited 
in  a muffle  furnace  up  to  900°  centigrade,  cooled,  and  weighed 
as  magnesium  py roar senate  ( Ugg  As 3 Oy  ) 


Sample 

$ As 

Sample 

$ As 

1 

13.74 

4 

— — 

13.08 

6.19 

2 

6 . 85 

5 

6.22 

7.31 

6.39 

3 

6.78 

6 

5.68 

7.42 

5.33 

. Determination  of 

ammonium 

content , 

One  third  gram  samples  were  dissolved  in  200  cc . of  water 
and  distilled  with  25  cc.  of  5$  (wt)  sodium  hydroxide  solution 


: 


. 

. 


. 


. 


. 


. 


. 


iJw*  I 1 1 1 1 I 


5* 

previously  boiled.  Distillation  was  continued  until  the  distil- 
late was  2/3  the  volume  of  the  original  solution.  The  distillate 
was  received  in  25  cc.  of  n/lO  solution  of  hydrochloric  acid  and 
the  excess  titrated  with  standard  sodium  hydroxide. 

Sample  $ NH^ 

1 2.4 

2.5 

2 4.6 

4.7 

3 5.1 

4.2 

4 4.3 

5.0 

3.  Determination  of  molybdenum  content. 

The  alkaline  filtrates  from  the  arsenic  precipitations 
were  used  for  the  molybdenum  determinations.  After  most  of 
the  free  ammonia  had  been  removed  by  heating,  the  filtrate  was 
neutralized  with  dilute  sulfuric  acid  and  evaporated  to  about 
100  cc.  Ten  cc.  of  dilute  sulfuric  acid  was  added  and  the  so- 
lution placed  in  a 300  cc.  oval  pressure  flask  which  had  a por- 
celain top  like  that  of  a citrate  of  magnesia  bottle.  After 
the  air  in  the  flask  ?<ras  partly  removed  by  the  application  of 
vacuum,  the  flask  was  connected  with  hydrogen  sulfide  under  pres- 
sure until  the  solution  was  saturated  with  the  gas.  The  stopper 
was  then  fastened  and  the  flask  placed  in  a water  bath  at  a 
temperature  of  from  60  to  80  degrees  centigrade  for  about  half 


6. 


an  hour . 

Filtration  through  an  asbestos  Gooch  crucible  proved  in- 
adequate as  the  molybdenum  sulfide  was  partly  in  the  colloidal 
state.  This  difficulty  was  overcome  by  heating  the  solution  for 
a longer  period  at  a slightly  higher  temperature  ( 80  to  IOC 
degrees  for  about  an  hour  and  allowing  to  stand  over  night).  It 
was  found  that  from  three  to  five  successive  precipitations  were 
necessary  for  the  complete  removal  of  the  molybdenum  from  the 
solution.  Incomplete  removal  was  evident  in  any  case  by  the 
blue  color  of  the  filtrate. 

Another  difficulty  was  now  encountered  in  that  some  of  the 
sulfide  in  the  crucible  was  oxidized  by  the  air,  in  the  interval 
between  filtrations,  to  soluble  compounds  which  were  washed 
through  into  the  filtrate  at  the  following  filtration.  It  was 
realized  that  a quantitative  separation  by  this  method  would  be 
impossible  without  more  elaborate  equipment,  either  in  the  way 
of  a reducing  atmosphere  for  the  precipitate,  or  the  employment 
of  fresh  Gooch  crucibles  for  each  filtration.  Thinking  this 
inadvisable,  the  writer  decided  to  employ  a different  method, 
namely;  of  filtering  each  time  through  a fresh  quantitative  fil- 
ter paper. 

After  drying  the  filter,  the  brownish-black  precipitate  was 
removed  as  well  as  possible  and  preserved  between  watch  glasses 
while  the  filter  paper  was  burned  in  a weighed  crucible.  The 
precipitate  was  then  added  to  the  crucible  and  ignition  to  the 
oxide  attempted.  This  step  in  the  process  proved  unsatisfactory. 
The  sulfide  was  found  very  prone  to  deflagrate  and  the  molybdic 


* 


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7. 

3 

acid  to  volitalize  as  stated  by  Mellor  . A number  of  the 
precipitates  were  ignited  and  in  each  case  it  proved  difficult 
to  maintain  the  proper  temperature,  for  with  too  small  a flame 
the  ignition  was  exceedingly  slow,  and  with  a slightly  larger 
flame  deflagration  took  place  unexpectedly  from  time  to  time. 
Moreover,  after  this  stage  was  passed  it  was  difficult  to  com- 
pletely convert  the  blue  residue  to  the  white  oxide  without  caus- 
ing some  volatization. 

A third  method  was  now  tried.  It  was  intended  to  ignite 

the  precipitate  with  a little  pure  sulfur  in  a current  of  ir/dro- 

4 

gen  by  means  of  a Rose  crucible  . Consequently  a Kipp 

hydrogen  generator  was  set  up  and  to  which  was  connected,  a 
wash  tower  containing  potassium  permanganate  in  concentrated 
sulfuric  acid,  a wash  tower  containing  40  per  cent  sodium  hydrox- 
ide solution,  and  also  a calcium  chloride  drying  tower.  However, 
at  this  time  it  was  found  impossible  to  get  complete  precipita- 
tion of  the  molybdenum,  sulfide,  as  previously.  It  was  attempt- 
ed with  solutions  of  sulfuric  acid  content  ranging  from  5 to 
60  cc  of  the  dilute  acid  in  150  cc.  of  solution,  but  in  each 

case  the  blue  color  of  the  filtrate  persisted. 

5 

A fourth  method  was  now  tried.  The  arsenic  was  first 
removed  as  before  by  precipitation  with  magnesia  mixture.  The 
excess  ammonia  was  neutralized  with  hydrochloric  acid.  A few 
drops  of  ammonium  hydroxide  were  added  and  then  2 or  3 cc.  of 
acetic  acid  ( 33  per  cent)  in  excess  and  the  solution  diluted 
to  200  cc . The  solution  was  boiled.  Boiling  was  continued 
while  40  to  50  cc . of  a lead  acetate  solution  ( 40  grams  of 


8. 


lead  acetate  crystals  per  liter)  were  added  and  then  for  four 
more  minutes  accompanied  with  vigorous  stirring.  The  precipi- 
tate was  allowed  to  settle,  and  then  was  filtered  thru  asbestos 
in  a Gooch  crucible  with  suction.  The  precipitate  was  washed  by 
decantation  with  a boiling  solution  of  25  grams  of  ammonium  chlor- 
ide and  ten  drops  of  acetic  acid  per  liter  until  free  from  lead. 
The  washings  were  tested  with  hydrogen  sulfide  for  lead. 

In  washing  by  decantation,  the  wash  solution  was  kept  a3 
hot  as  possible  and  the  mixture  stirred  vigorously  before  each 
decantation.  After  being  washed  free  from  lead,  the  precipitate 
was  washed  twice  with  boiling  water.  The  crucible  was  heated 
on  an  asbestos  plate  until  dry  and  then  over  a free  flame.  It 
was  cooled  and  the  precipitate  weighed  as  ?b  Mo  O4. 


Sample 


1 


2 


47.29 


48.36 


3 


49.42 


48.21 


4 


51.17 


51.34 


5 


46.16 


46.10 


4.  Determination  of  moisture  content 


For  this  determination  samples  were  heated  in  an  electric 


oven 


, 

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- 

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. 

IlflH 

. 


. 


. 


. 


Sample  /&loss  at 

100°C 

9s 

$ loss  at  110°C  <fo  loss  at  150°C 

1 

1.27 

1.77 

2.38 

2 

4.06 

5.21 

6 .06 

3 

2.87 

3.70 

4.53 

4 

1.68 

2.33 

3.30 

Calculations 

The  following  calculations  were  made  from  the 

data  obtain- 

e&  by 

the  analyses  in  order 

to  determine  formulae, 

if  possible: 

( Percentages  figured  on  samples  as  obtained) 

foMo 

folloOZ 

$ As 

i°  as20S  $ hh4 

Total  $ 

47.34 

71.01 

13.08 

20.05  2.5 

93.56 

47.29 

70.93 

6.85 

10.50  4.6 

86.03 

48.36 

72.54 

7.31 

11.21  4.7 

88.45 

49.42 

74.13 

6.78 

10.39  5.1 

89.62 

48.21 

72.31 

7.42 

11.38  4.2 

89.89 

51.17 

76.75 

— 

4.3 

— 

51.34 

77.01 

6.19 

9.49  5.0 

91.50 

46.16 

69.24 

6.22 

9.54 

— 

46.10 

69.15 

6.39 

9.80 

— 

^MoC'3 

r-  144  /iASgOg-i- 

230 

Peat  io 

$NH4*  18  M0O3  As205 

nh4 

.4931 

.0871 

.1389  5.66  1 

1.59 

.4926 

.0456 

.2556  10.80  1 

5.60 

.5038 

.0487 

.2611  10.34  1 

5.36 

.5148 

.0451 

.2833  11.42  1 

6.28 

.5022 

.0494 

.2333  10.17  1 

4.72 

.5348 

.0412 

.2778  12.93  1 

6.74 

10.. 


#Mo 

( Percentages 
$Mo03  joke 

figures  on 
jo  A s 2 0 5 

samples  dried  at 
f»KH4 

110°C) 

Total 

48.19 

73.28  13.32 

20.42 

2 .54 

95.24 

49.89 

74.83  7.22 

11.07 

4.85 

90.75 

51.03 

76.53  7.71 

11.82 

4.95 

93.30 

51.32 

76.98  7.04 

10.79 

5.29 

93.06 

56.06 

75.09  7.70 

11.80 

4.36 

81.2  5 

53.39 

78.59 

— 

— 

— 

52.57 

78.85  6.33 

9.70 

5.11 

93.66 

ybMoO^  t 

144  foAsgOg  * 230 

$1TH4  -r  18 

Ratio 

MoOg  AsgOg 

nh4 

.5030 

.088.7 

.1411 

5.65  1 

1.58 

.5197 

.0481 

.3694 

10.80  1 

5.58 

.5315 

.0514 

.2750 

10.34  1 

5.35 

.5346 

.0409 

.2939 

11.39  1 

6.26 

.5215 

.0513 

.2422 

10.16  1 

4.72 

.5476 

.0421 

.2839 

13.98  1 

6.70 

IV 

Arseno-LIolybdic  Acid  as  a Qualitative  Reagent  For 

Alkaloids . 

Solutions  of  the  alkaloids  quinidine,  cinchonine  and 
cinchonidine  in  hydrochloric  acid  were  prepared  and  to  each  was 
added  arsenomolybdic  acid  solution  ( a solution  of  the  ammonium 
salt  in  dilute  hydrochloric  acid)  until  the  precipitation  was 
complete,  and  then  an  excess  added.  The  treatment  of  the  clear 
filtrate  with  Mayer's  reagent  gave  no  precipitate  or  cloudiness 


I 


11 


to  the  solution. 

Samples  of  salts  prepared  in  this  work  were  heated  over 
a wide  range  of  temperature,  starting  at  one  hundred  degrees 
centigrade.  Color  changes,  were  observed,  which,  altho  not 
bearing  directly  on  the  subject  of  this  work,  were  quite  interest- 
ing. The  writer  has  attempted  to  describe  these  color  changes  in 
tabular  form,  and  the  temperature  given  are  approximate. 


Sample 

100° 

105° 

lighter 

125° 

185° 

white  to 

190° 

1 

yellow 

yellow 

dark 

wh  it  e 
pale 

pale  green 

pale  green 

2 

ii 

yellow 

yellow 

orange 

" yellow 

" orange 

3 

it 

it 

yellow 

orange 

deep  orange 

4 

ti 

it 

ii 

n 

deep  orange 

210° 

230° 

250° 

2 70° 

pale  green 

dark  green 

1 

pale  green 

to  brown 

green  brown 

to  brown 

2 

orange  to 
green 

orange 

green 

and 

myrtle  green 

myrtle  green 

orange  to 

orange 

and 

myrtle  green 

myrtle  green 

3 

green 

green 

orange 

and 

dark  orange 

dark  orange 

4 

orange 

green 

and  green 

and  green 

300° 

asbest1 

os  gauze 

3 in. 

flame 

4 in.  flame 

1 

shiny  brown 

deep  green  ) 

shinny  brown 

)all 

2 

green  brown 

yellow 

green) smoke 

dark  green 

)and 

3 

green  brown 

yellow  green) give 

dark  green 

) of  f 

4 

green  brown 

orange 

green; fumes 

dark  green 

* 


. 


. 


* 


12 


Sample 

5 

in.  flame 

red  heat 

when 

. cool 

1 

dark 

blue  green 

orange  yellow 

shinny 

silver 

fthite 

2 

moss 

green  to  blue 

yellow 

sh inny 

silver 

white 

3 

moss 

green  to  blue 

yellow 

shinny 

silver 

white 

4 

moss 

green  to  blue 

yellow 

sh inny 

silver 

white 

V 

Conclusions 

It  is  believed  that  from  the  results  of  this  work  the 
following  conclusions  may  be  drawn; 

1.  That  the  ammonium  salt  of  an  arsenornolybdic  acid  was 
prepared . 

2.  That  by  treating  ammonium  molybdate  in  acid  solution 
with  sodium  arsenate  one  complex  was  formed,  while  by  salting 
out  from  the  same  solution  a different  complex  was  formed. 

3.  That  of  the  samples  prepared  the  first  has  probably 
one  formula  and  the  others  another  formula.  The  samples  pre- 
pared were  not  purified  and  consequantly  from  the  data  obtained 
by  the  analyses  it  is  not  possible  to  conclude  definite  formulae. 

4.  That  the  arsenornolybdic  acids  prepared,  or  their  salts 
in  acid  solution,  are  quantitative  precipitants  for  alkaloids. 


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